Quantification and comparison of the nonlinear mechanical properties of transcutaneous and human aortic valve leaflets: Experimental and numerical studies

Background: Extracting the mechanical behaviors of tissue leaflets in prosthetic aortic valves is necessary for designing and manufacturing appropriate prostheses for percutaneous deployment. The goal of this study was to opt a proper tissue for bioprostheses.Methods: In this study, donkey and bovine pericardia and human aortic valve leaflets are compared mechanically. The uniaxial and biaxial tensile tests were performed on the tissue specimens. The measured uniaxial data were then fitted into Yeoh, and Mooney-Rivlin hyperelastic models, and the elastic modulus, failure strain, and ul-timate tensile strength (UTS) for each sample were calculated. Furthermore, to determine the degree of anisotropy of the specimens, the biaxial hyperelastic properties of the samples were extracted using the Gasser-Ogden-Holzapfel (GOH) and Mooney-Rivlin models. In addition, the extracted anisotropic parameters were exerted to the finite element modeling of the bovine and donkey pericardia.Results: Donkey pericardium exhibited a low stiffer behavior, based on its lowest strain energy magnitude and the average slope of stress-stretch curves. This tissue was also high distensible than the bovine pericardium, due to its highest areal strain. Furthermore, the donkey finite element model induced low stress regions during the systole and diastole phases. On the other hand, decreased mechanical stress on the bioprosthetic leaflets may reduce tissue dehiscence and increase the long-term durability of the valve. Conclusion: The nonlinear behavior of the pericardial tissues can be well-characterized by the constitutive functions. The mechanical properties of the donkey pericardium are even closer to the native leaflets. The donkey pericardium might be a good candidate valve leaflet material for bioprostheses.